Method for treating containers

ABSTRACT

Rectangularly shaped container are stacked within each other and advanced along a horizontal path through a treating station where changes are effected along two of the opposing sides of each container in the stack. The stack is then pivoted 90o in a special manner while remaining seated on the surface of a conveyor by means of an obstruction in the path of travel and a guiding surface mounted at an angle to the path, whereupon the stack is then advanced further in the same direction through another treating station to effect changes along the other two opposing sides of each container in the stack.

P 1974 s. H. PRUDEN 7 METHOD FOR TREATING CONTAINERS 2 Sheets-Sheet 1 Filed May 9, 1969 INVENTOR. SAMUEL'H'. PRUDEN BY y z r ATTORNEY.

April 30, 1974 s. H. PRUDEN 3,808,301

METHOD FOR TREATING CONTAINERS Filed May 9, 1969 2 Sheets-Sheet 2 FIG.2 4o qg/ FIG. 3 q? I I l 1 m I W" Mn Q'h W- flflm W M- II "wh A INVENTOR. SAMUEL H. PRUDEN ATTORNEY:

United States Patent Oifice Patented Apr. 30, 1974 3,808,301 METHOD FOR TREATING CONTAINERS Samuel H. Pruden, East Hartford, Conn., assignor to Monsanto Company, St. Louis, Mo. Filed May 9, 1969, Ser. No. 823,453 Int. Cl. B29c 25/00; B29f 5/00 US. Cl. 264-80 4 Claims ABSTRACT OF THE DISCLOSURE Rectangularly shaped containers are stacked within each other and advanced along a horizontal path through a treating station where changes are effected along two of the opposing sides of each container in the stack. The stack is then pivoted 90 in a special manner while remaining seated on the surface of a conveyor by means of an obstruction in the path of travel and a guiding surface mounted at an angle to the path, whereupon the stack is then advanced further in the same direction through another treating station to effect changes along the other two opposing sides of each container in the stack.

BACKGROUND OF THE INVENTION This invention relates to the treatment of containers and more particularly to an improved method and means for orienting containers between successive treating stations.

In recent years there has been ever increasing utilization of thermoformed containers of synthetic plastic material for various packaging applications. Among the most widely utilized container forms are trays which may be overwrapped with a film of synthetic plastic to provide an attractive and hygienic container affording the opportunity to display the contents either partially or entirely if the tray is formed of a transparent material.

As is well known, various techniques are employed for the thermoforming and finishing of the containers from the basic sheet stock. From the standpoint of speed and economy of operation, the thermoforming technique which has achieved widespread application involves forming the container depressions in a long length of the sheet material at one stage, usually several across the width of the sheet material, by means of multicavity dies, and using the web between the container cavities to carry the partially formed containers to a subsequent stage where the sheet material is treated to separate the container from the web about them. Generally, the forming dies include cooperating surfaces providing a cutting knife edge and a bed to cut substantially through the thickness of the synthetic plastic so that the tray forms may be separated from the web at a subsequent stage simply by flexing the sheet or otherwise applying a separating pressure.

Since the cutting dies tend to wear and since the material is, in fact, not cut through cleanly at the time of separation, there is a tendency for the crushing and fracturing to produce jagged edges, whiskers and other particles of the synthetic plastic along the edge or flange of the container.

This tendency is particularly pronounced when the material is biaxially oriented to achieve great strength at a relatively low cost per pound of material. The jagged edge of the container represents a potential problem in that it may subsequently cut through a film overwrapped about the container, and this resulting exposed edge may then damage the film overwrap of an adjacent package in the same manner. The whiskers may be unpleasant to the touch of the customer. Moreover, particles of plastic adjacent the edge may contaminate the contents of the container or provide a gritty feel to a customer.

Any additional steps to be performed on the trays to eliminate the problem of slivers and crushing are desirably carried out outside of the type of existing thermoforming equipment which makes use of the web of sheet material as a carrier for the molded containers and at a speed sufficient to avoid any delay in upstream high speed thermoforming operations. Elimination of the problem during thermoforming in such a manner as would eliminate the web as a carrier material is accordingly undesirable.

In copending US. application Ser. No. 777,030, filed Nov. 19, 1968 now Pat. No. 3,578,734 granted May 11, 1971, and assigned to the assignee of the present invention, there is described a method and apparatus for eliminating the problem by flame treating the edges of such containers when in rectangular form to convert the jagged edges into a rounded thickened section. This technique involves successively conveying stacks of these containers along a right angle path, with two sides of the containers treated along each leg of the path. A switching device is interposed at the intersection of the two legs for transferring each stack from one conveyor to another. Though this approach generally accomplishes the desired result in terms of treatment of the containers, it has a number of disadvantages related to handling of the stacks. The mechanism for transferring the stacks between conveyors is pneumatically operated and susceptible to wear after repeated use, thereby reducing reliability and making it diflicult to control the rate of transfer of the stack. This often causes a backup of stacks on the first conveyor or causes a rough transfer which results in misalignment of a stack on the second conveyor and accordingly an uneven treatment of the containers of that stack in the second treating station. A pocket of wasted, valuable fl'oor space exists because of the right angle orientation of the apparatus, which configuration renders it difiicult, and in some cases even impossible, to fit the equipment into existing plants. The reciprocating transfer mechanism must reposition itself each time before the next stack of approaching containers can be transferred to the second conveyor, thus incrementally affecting the capacity of the equipment. Also, the dual conveyors and transfer mechanism add to the capital and maintenance cost of the equipment.

Now there has been developed a new technique for orienting stacked containers between treating stations which overcomes these shortcomings of the prior art.

Accordingly it is an object of this invention to provide an improved method for treating containers nested together within a stack. 7

An additional object of this invention is to provide an improved method for consecutively exposing pairs of container sides positioned at to each other to treating equipment.

A further object of this invention is to provide a method for rotating a stack of rectangular containers while resting on the surface of a moving horizontal conveyor to expose a second pair of sides to treating apparatus aligned with that for treating the first pair of sides.

Another object of this invention is to provide a method for rotating rectangular containers 90 between treating stations which is designed to be continuously available to handle consecutively approaching stacks without requiring repositioning after each stack rotation.

Another object of this invention is to provide a technique for treating the flanges of synthetic plastic containers to provide a substantially smooth, beaded outer edge thereon, wherein the apparatus involved is reliable, is adapted to high speed, economical operation, uses a reduced number of components, and wherein the floor space used to accomplish treating is optimized.

Other objects of this invention will in part be obvious and will in part appear hereinafter.

3 SUMMARY OF THE. INVENTION These and other-objects are accomplished in a method of treating containers having pairs of opposing sides, each side having a laterally projecting flange about at least a portion of its periphery, by initially stacking a multiplicity of such containers within each other, advancing the stack in a horizontal direction through a first treating station to physically change the edge portions of the flanges of one of the pairs of opposing sides of the containers, obstructing the advancing horizontal movement of a portion of the stack of containers after its passage through the first treating station while continuing the advancing horizontal movement of the remainder of the stack to orient the stack at an acute angle with respect to the direction of horizontal movement, rotating the oriented stack in the direction of horizontal movement through an angle complementary to the acute angle to position the second pair of opposing sides parallel to the direction of horizontal movement and continuing the horizontal movement of the stack in the same direction to advance the stack through a second treating station to physically change the edge portions of the flanges of a second pair of opposing sides of the containers.

The apparatus includes an obstacle intermediate the means for treating the pairs of opposing sides, which is situated within the outer limit of one side of the path of travel of the stack, this obstacle serving to partially obstruct movement of the stack along this path, and an elongated surface downstream of the obstacle which extends within the outer limit of the other side of the path for frictionally engaging and rotating the stack on the surface of the conveying means after its obstruction. The obstacle is preferably an elongated abutment above the conveying means and positioned parallel to one of its sides, the trailing end of the abutment serving to limit the extent of lateral movement of the stack across the conveyor by the elongated guiding surface. The elongated guiding surface is preferably an endless, rotating conveyor above the surface of and at an angle to the direction of the conveying means.

BRIEF DESCRIPTION OF THE DRAWINGS In describing the overall invention, reference will be made to the preferred embodiment illustrated in the accompanying drawings in which:

FIG. 1 is a plan view of apparatus embodying the present invention showing stacks of trays at various points along the path of travel through the apparatus;

FIG. 2 is a sectional elevational view taken along the line 2-2 of FIG. 1;

FIG. 3 is a view similar to FIG. 2 taken along the line 3 3 of FIG. 1;

FIG. 4 is a partial plan view of the apparatus of FIG. 1 illustrating the manner in which a stack is rotated;

FIG. 5 is a partial, diagrammatical, elevational view of a treating section of the apparatus illustrating treatment of a stack of trays along one side thereof;

FIG. 6 is an enlarged, fragmentary section view of a single tray showing the flange with a typical jagged edge and particles on its surfaces; and

FIG. 7 is a view similar to FIG. 6 showing the flange after flame treating.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT With reference to the drawings, there is shown in FIG. 1 appartus generally indicated as 10 for treating containers 12 having pairs of opposing sides 14a and 14b, each side having a laterally extending flange 16 about at least a portion of its periphery. Apparatus 10 includes means for conveying a stack 22 of containers 12 of synthetic plastic material along a substantially horizontal path, which includes an endless horizontal object transporting conveyor 20 adapted to rotate about conventional rollers by pulley units typically indicated as 17. Conveyor 20 has a continuous surface 18 for transporting a stack 22 of containers 12 along the horizontal path defined by conveyor 20. Feed table 13 precedes conveyor 20.

Apparatus 10 further includes means 24 disposed along opposite sides of the horizontal path defined by conveyor 20 for concurrently treating sides 14a of rectangular containers 12 of stack 22. Means 24 comprises two opposing burners 26 providing flames 28 directed at an acute angle to the horizontal path of movement of each stack. Burners 26 may be fixedbut preferably are adjustably mounted by suitable means on side brackets (not shown) and are supported on frame 32 of apparatus 10 so that they may be moved inwardly or outwardly with respect to conveyor 20. By controlling the pressure in the feed lines 31 and the lateral adjustment of the burners, flame 28 is caused to contact the outer edge portion of flanges 16 of trays 12 of stack 22 passing thereby. As best seen in FIG. 5, flame 28 is limited in the depth of penetration between adjacent flanges 16, but does act on their outer edge portions to eliminate jagged edges and whiskers 34 (FIG. 6) of plastic therefrom. The angular disposition of burners 26 serves to limit the depth of penetration of flame 28 inwardly between flanges 16, while at the same time insuring a relatively broad scope of action upon the outer edge of flanges 16 associated with sides 14a.

To minimize the effect of air currents upon the operation of burner units 26 and to protect the operator of the apparatus, heat shields 36 are provided outwardly of the sides of conveyor 20. To facilitate adjustment, heat shields I 26 may be slidably mounted on support bars (not shown) which in turn are mounted on a portion of the apparatus frame 32.

Downstream of the means 24 for concurrently treating flanges 16 associated with two of the four sides of rectangular containers 12, is an abutment 40 fixedly mounted on frame 32 and positioned slightly above surface 18 of conveyor 20. Abutment 40 comprises a rail portion 42 extending parallel to and within the outer limit of side 44 of the horizontal path defined by surface 18 of conveyor 20. Abutment 40 further comprises an obstructing or obstacle portion 46 extending substantially perpendicular to and connected to one end of rail portion 42, which end is closest to the means 24 for treating sides 14a of containers 12.

Opposite abutment 40 (FIG. 3) and extending downstream of obstacle portion 46 and at least partially within the outer limit of the other side 45 of surface 18 of conveyor 20 there is provided an elongated surface for frictionally engaging and guiding or turning a portion of stack 22 after obstruction by obstacle portion 46 of abutment 40. This surface preferably is endless surface 50 of conveyor 48 positioned slightly above horizontal surface 18 of conveyor 20, which rotates about a vertical axis at an acute angle to, and in the same direction as the direction of movement of the stacks being transported by conveyor 20. Conveyor 48 is caused to rotate about rollers 49 by suitable conventional drive means (not shown). Movably mounted idler roll 51 may be provided to adjust the tension of surface 50. Contact surface 50 is considerably shorter in overall length than that of surface 18 of the main transporting conveyor 20 since it has a stack turning rather than transporting function. For example, the overall length of endless surface 50 is generally between 25 to 50% of that of conveyor 20.

Situated downstream of conveyor 48 and rail portion 42 of abutment 40 are means 52 disposed along opposite sides of conveyor 20 for concurrently treating the flange 16 associated with the other two sides 14b of rectangular containers 12 in stack 22. These means 52 comprise adjustably mounted burners having flames directed at an acute angle to axis 55 of conveyor 20 and which are constructed, arranged and function in the same manner as previously described burners 26. Though means 24 and 52 are illustrated as being identical, so that the flange associated with each pair of opposing sides undergoes identical treatment,

they obviously could be different in situations where it is desired to treat one pair of sides in a manner different from the other pair. Similarly, one side of a pair may be treated differently from that of the other side of the pair.

Heat shields 54 on either side of conveyor 20 are provided downstream of means 52, and which function, are constructed and mounted identically to previously described heat shields 36.

In operating the illustrated apparatus 10, stack 22 is initially formed by nesting a plurality of containers 12 within each other, containers 12 having angularly outwardly disposed side walls 15 (FIG. 6), such that when one container is nested within another, portions of side walls 15 of adjoining containers abut against each other, thereby providing a space 17 between laterally extending overlying flanges 16 of the containers. Stack 22 is moved off the surface of feed table 13 onto surface 18 of conveyor 20, either manually or automatically by means of a switch operated transfer unit of the type generally depicted in copending application Ser. No. 777,030, filed Nov. 19, 1968. When placed on conveyor 20, the lowest container in the stack frictionally contacts surface 18 of the conveyor, and the stack is oriented such that sides 14a of the containers are parallel to axis 55 of conveyor 20. Surface 18 of conveyor 20 is moved forward horizontally to advance stack 22 between flames 28 of opposing burners 26 to expose flanges 16 to these flames for an abbreviated time in order to produce a bead 58 ('FIG. 7) of increased thickness on the outer edges of the portions of flange 16 which extend along opposing sides 14a of rectangular containers 12. As a result of the effect of the heat in producing fusion and/or deorientation (relief of stresses previously induced in the synthetic plastic material of the tray) the flange should be physically altered in configuration to provide a bead about 50-150 percent greater in thickness than the unaltered material of the flange adjacent thereto. Such a physical change will normally indicate that the jagged edge and any whiskers or other particles immediately adjacent the edge have been involved to provide the desired smooth surface to the touch. The flame will usually produce fusion of whiskers and other small particles with which it comes into contact and may or may not produce fusion of the edge portions dependin upon whether deorientation is relied upon to effect the physical change.

As surface 18 continues to advance horizontally, a portion 60 of leading side 62 of the advancing stack, which portion (FIG. 1) is adjacent the intersection of this leading side with one of the two previously flame exposed sides 14a, strikes against obstructing portion 46 of abutment 40, while conveyor surface 18 continues its advancing horizontal movement. This action causes stack 22 to become oriented on conveyor surface 18 at an acute angle with axis 55 of conveyor 20 or with the horizontal path defined by the direction of movement of conveyor 20. The continued horizontal movement of the conveyor surface, however, causes the other end of the leading side of the stack to advance beyond obstacle 46, and immediately brings corners 64 of the containers within the stack, which corners are diagonally opposite the intersection between the leading side and one of the two flame exposed sides 14a, into frictional contact with endless surface 50 of conveyor 48. Surface 50 is generally positioned at an angle of from to 50 with the horizontal, and is moving in the direction of movement of stack 22. This frictional contact with moving surface 50 of conveyor 48 moves leadin side 62 of stack 22 against rail portion 42 of abutment 40 which extends parallel to the horizontal, thereby completing the 90 rotation of the stack 22 from its initial position on the conveyor surface upstream of burners 26. Each stack is moved through an angle t? which is complementary to angle 0 across surface 18 of the conveyor and against rail portion 46 of abutment 40. Rail portion 46, therefore, serves to delimit the angular movement of stack 22 through angle ,6. The angle C of surface 50 of conveyor 48 with the horizontal direction of movement is maintained at between 10 to 35 for optimum results. To achieve the pivotal type of movement of the stack, the force generated on the lowermost container in the stack by the advancing conveyor must be greater than the frictional force between the lowest container in the stack and the supporting portion of the conveyor surface. As can be seen from FIG. 1, before any one stack has had its last two sides flame treated, the next successive stack to be treated is undergoing rotation.

Surface 18 of conveyor 20 then continues its horizontal movement to advance the rotated stack thereon between the two additional flames of treating means 52 which are directed against the portion of flange 16 associated with the other two sides of the stacked rectangular containers 12, to expose the portion of flange 16 associated with sides 14b for an abbreviated time to produce a bead 58 of increased thickness on the outer edge of the portion of flange 16 associated with sides 14b.

After stack 22 moves between heat shields 54 downstream of burners 52, they may be either manually or automatically removed from apparatus 10 for packin or further processing as required.

The above description and particularly the drawings are set forth for the purpose of illustration only and are not to be taken in a limited sense.

The present invention is applicable to the treatment of containers having at least two pairs of opposing sides, all or portions of which it is desired to have treated to effect changes therein. Most usually, the containers will be thermoformed from synthetic plastic sheet material in order to achieve fabrication at the greatest possible rates of speed and with the greatest economy. The sheet material may be biaxially oriented for strength prior to thermoforming or it may be oriented by the forming operation itself. The container configuration must be rectangular in cross section although it may have rounded corners. The technique of the present invention is also applicable to injection molded or blow molded containers to remove flash and other projecting portions about any flange provided thereon.

Operability of the container rotating portion of the system of the invention is a function of the coeflicient of friction between the container and the surface of the conveyor. Theoretically the system should be able to accurately orient a single shallow rectangular tray of synthetic plastic when a conveyor surface having the proper frictional surface characteristics is chosen. In actual practice, however, due mainly to the vibration of conventional operating equipment components, it has been found that additional weight is necessary in order to have the containers remain on the transporting conveyor surface in the desired positions. This is preferably achieved in the case of trays of synthetic plastic each approximately 0.5-0.75 inch deep, by stacking at least five and preferably between 10-15 of these trays together, with a tray spacing within the stack of about A inch. The upper limit of the number of such trays in a stack is basically determined by the stability of the stack on the moving conveyor surface. Up to of such trays may be stacked together without toppling.

Though the guiding or turning surface for frictionally contacting and turning the angularly oriented stack on the transporting conveyor surface is shown as moving in the preferred embodiment, it may be stationary if the coeflicient of friction between the guiding surface and the surface portion of the stack with which it comes into contact is sufliciently low, and the angle of this surface with the horizontal is maintained at less than 30. This angle C for a stationary surface is determined by the relationship between the frictional force which drives the object being turned (i.e. that between the transporting conveyor surface and the lowermost tray in the stack) and the force introduced by the angle of the guiding surface. For a stationary guide surface, this must be rather critically established and maintained for a given container size, usually at between to 30". Though this angular range still applies, considerably more versatility is obtained with respect to angular positioning of this surface when it is moving as in the preferred embodiment, in that C may be any acute angle and the system will still be operative.

Though an elongated abutting surface is shown opposite the guiding or turning conveyor in the preferred embodiment for delimiting the extent of movement of the angularly oriented stack across the conveyor surface, this may not be necessary if high speed processing is not required. Under such circumstances, the guidin conveyor may be operated slowly so as to avoid driving the stack excessively outwardly out of alignment with the conveyor axis. A pin positioned in the path of movement of the stack and within the outer edge of the transporting conveyor functions satisfactorily as the obstacle when an elongated abutting surface is not used.

The speed of the turning conveyor is a function of C, i.e. the angle which its contacting surface makes with the horizontal. Though this speed may be greater than, less than or equal to the surface speed of the main transporting conveyor supporting the stack, it preferably exceeds the surface speed of the main conveyor by an amount equal to the velocity of the surface of the main conveyor divided by cosine C.

The main object transporting conveyor can be operated at speeds up to 125 f.p.m. to provide the desired flange treatment without adversely affecting turning mechanism performance. The object turning or guiding surface speed is inversely related to the cosine of the angle C, with an optimum operating speed being equal to main conveyor surface speed/cos C. Speeds of 100 to 150% of the main conveyor speed provides satisfactory results.

The function of the preferred turning conveyor is to impart rotation to the object(s) being transported. Consequently its surface must be perpendicular to the surface of the main conveyor and preferably located above but with its lower edge close to the surface of the main transporting conveyor in order to accommodate relatively short objects or stacks. The vertical height of its contacting surface must be sufficient to provide suflicient contact with the preferred tray edges in the stack to avoid having the moving stack topple over it. The width (vertical direction) and position of the contacting surface portion of the turning conveyor is preferably such as to contact the tray edges which are in the center portion of the stack, though this width may be from 50 to 125% of the total height of the stack.

In the preferred embodiment, the total amount of heat imparted to the container flange and the surface area with which the flame comes into contact must be closely controlled to avoid excess fusion and/or deorientation of the synthetic plastic material. By providing the trays with a spacing of about & to inch between the flanges of adjacent trays, the penetration of the flame inwardly from the edge can be limited to a beneficial degree. In addition, the volume of material provided by such stack serves as a heat sink to minimize localized overheating as a result of a transient effect despite the relatively poor heat conductivity of the material.

The method ofthe present invention is broadly applicable to the treatment of any object(s) having dual pairs of sides mounted at right angles to each other. The rotating portion of the apparatus could be applied to turn "an object for subsequent handling or to feed to another machine of an automated line. The apparatus utilized is mechanically simple, and is generally oriented in one direction thereby utilizing a minimum of floor space. Equipment components are reduced and reliability and treating capacity are increased over that of the prior art. The equipment may rotate successively advancing stacks without'requiring a repositioning movement prior to acting on successive stacks.

' It will be understood that many variations and modifications of the embodiments herein described will be obvious to those skilled in the art and may be carried out without departing from the spirit and scope of the invention.

What is claimed is:

1. In a method of treating containers having pairs of opposing sides, each side having a laterally projecting flange about at least a portion of its periphery, said method comprising:

(a) nesting a multiplicity of said containers together to form a vertically oriented stack;

(b) advancing said stack in a horizontal direction through a first treating station to physically change the edge portions of the flanges of one of the pairs of opposing sides of the stacked containers;

(c) obstructing the advancing movement of a portion of the stack of containers after its passage through the first treating station without changing the vertical orientation of the stack, while continuing the advancing horizontal movement of the remainder of the stack to orient the stack at an acute angle with respect to the direction of horizontal movement;

(d) rotating the oriented stack by frictionally engaging a corner of the oriented stack with a surface moving in the general direction of and at an angle to the horizontal movement of the stack in the direction of horizontal movement through an angle complementary to the acute angle to position the second pair of opposing sides parallel to the direction of horizontal movement; and

(e) continuing the advancing horizontal movement of the stack in the same direction through a second treating station to physically change the edge portions of the flanges of a'second of said pair of opposing sides of said containers.

2. The method of claim 1 wherein the angle of the surface with the horizontal movement is between 10 to 35.

3. In a method of treating rectangular synthetic plastic containers having flanges extending laterally outwardly from each of their four sides, said method comprising:

(a) stacking a multiplicity of said containers in nested relationship to provide space between their flanges;

(b) placing the stack on the surface of a conveyor with two of the sides of the stacked containers parallel to the axis of the conveyor surface to frictionally engage the lowest container in the stack with the surface of the conveyor;

(c) moving the surface of the conveyor horizontally to advance the stack in place thereon between two flames directed against the flanges of said two of the sides of the stacked containers to expose said flanges of said two sides to said flame for an abbreviated time to produce a bead of increased thickness on the outer edges of the flanges of said two sides;

(d) striking a portion of the leading side of said advancing stack, which portion is adjacent the intersection of the leading side with one of said two flame exposed sides, against an obstruction while continuing horizontal movement of said conveyor surface to angularly orient the stack on the conveyor surface;

v (e) frictionally engaging the corners of the containers in the stack which are diagonally opposite said intersection between the leading side and one of the two flame exposed sides with a surface moving at an angle of from 5 to 50 with the horizontal to move said leading side of the stack against a fixed surface 9 10 extending parallel to the horizontal to thereby rotate against the obstruction is greater than the frictional force the stack 90 from its initial position on the coubetween said lowest container in the stack and the conveyor surface; arid veyor surface. (f) continuing horizontal movement of the surface of References Cited the conveyor to advance the rotated stack thereon between two additional flames directed against the 6 UNITED STATES PATENTS flanges of the other two sides of said stacked rec- 1 290 62 1 1919 Adderson 19 33 2 tangular containers to expose the flanges of said 7 5 497 11/1929 Duty 5 other two sidesfor an abbreviated time to produce a head of increased thickness on the outer edges of 1 DONALD J. ARNOLD, Primary Examiner the flanges of said other two sides. P 4 The method of claim 3 wherein the force generated KUCIA Assistant Exammer by the advancing conveyor on the lowest container in Us CL the stack immediately after said striking of the stack 234 345 

